1. Field of the Invention
This invention relates to a ratchet wrench, more particularly to a pneumatic ratchet wrench with a pneumatically actuated reversing device for selectively driving a drive body in a clockwise or counterclockwise direction.
2. Description of the Related Art
Referring to FIG. 1, a conventional pneumatic ratchet wrench 1 such as that disclosed in U.S. Pat. No. 6,640,669B2 generally includes a ratchet housing 11 and a drive spindle 12 which is disposed transverse to the ratchet housing 11 and which is unidirectionally rotated by means of a ratchet unit 17 for fastening or loosening a fastener engaged therewith through transmission and conversion of the rotation of an output shaft of an air motor (not shown). A direction reversing device includes a gear 13 which is rotatably mounted on the ratchet housing 11, and two arms 14 which are respectively attached to two buttons 15 to be moved alternately to engage the gear 13 in response to operation of the respective buttons 15, thereby permitting rotation of the gear 13 in a corresponding direction. The arms 14 are connected respectively by springs 16 to the ratchet housing 11 to bias the respective arms 14 away from the gear 13.
Since it is needed to apply a manual force to operate the selected button 15 during the fastening or loosening operation, and since the manual force applied is in a direction parallel to the direction of movement of the selected arm 14, the manual force has to counter the biasing action of the corresponding spring 16 and overcome the frictional resistance generated as a result of engagement between the corresponding arm 14 and the gear 13. Thus, the fastening or loosening operation is laborious and inconvenient to conduct.